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The present invention relates generally to the measurement of liquid volume. Specifically, the present invention relates to the measurement of liquid volume using the static pressure of the liquid to be measured.
The problem of measuring fluids is one of long-standing. The amount of fluid in a contained volume, such as a tank or reservoir, can be critical in commercial exchange, transportation, or any of a variety of endeavors. Measurement techniques range in sophistication from simply visually inspecting the liquid, to using a float or dipstick to physically indicate the level of fluid, to employing lasers or magnetic resonance to sense quantity or levels.
Not surprisingly, many measurement arrangements are represented in the patent literature. For example, U.S. Pat. No. 5,802,910 to Krahn, et al. is directed to a measuring system for liquid volumes that measures the liquid volume of a liquid or liquids held in one or more containers. This apparatus has no moving parts and includes an open-ended dynamic pressure tube standing in each container with its open tube end at the lowest point of the container on the bottom surface of it and a pressure measurement converter closing the other tube end so as to form an air column between the pressure measurement converter and a liquid level in it. The apparatus also includes an electronic analyzing device including an electronic circuit connected electrically to the pressure measurement converter and producing an electronic signal characteristic of a liquid volume in the container and a digital meter for displaying a volume reading.
U.S. Pat. No. 6,029,514 to Adam discusses a device for measuring and monitoring the volume of liquid in a container. An adapter for mounting the device is in an opening in the top wall of the container. The adapter supports a beam onto which one end of a float is connected such that the free end of the float extends substantially vertically into the container. A strain gauge is disposed on the beam so that the measuring direction of the gauge is parallel to the main axis of the beam. The device can also include a sensor for measuring physical parameters of the container. A processor is connected to the strain gauge and any sensor to take data from those input devices. During a calibration operation, a measurement function is derived to correlate strain gauge readings to the volume of liquid in the container. The function is recorded in a processor which takes data from the strain gauge and calculates the actual volume of liquid in the container. An output component displays the measurement. The device can be used in new containers and easily retrofitted to existing ones since the internal shape of the container is expressed in the measurement function.
U.S. Pat. No. 5,979,233 to Green shows a measuring arrangement in which an ultrasonic apparatus determines the fluid depth, volume, and temperature in a storage tank. A system description for monitoring an underground storage tank containing gasoline is described. The system determines the water""s and gasoline""s depth, volume, and temperature. The apparatus consists of a remote console, ultrasonic probe, and interconnecting cable. The remote console contains a display to report tank information and a computer to operate the probe. The probe consists of an ultrasonic transducer above the bottom of the probe facing upwards to transmit and receive ultrasonic signals, vertically spaced reflectors and a temperature sensor to measure fluid temperature.
U.S. Pat. No. 6,073,233 to Tan is directed to method and a device for capacitive liquid level measurement which are particularly suitable for determining liquid level between adhesive media of different conductivity. The known sensor principle is based on the fact that the environmentally dependent capacitance is measured between neighboring electrodes of a rod-shaped probe. According to the invention, the probe has electrodes with covers of different thicknesses. The effective thickness of an insulating pollutant film can then be determined by capacitance measurements between at least two pairs of electrodes. The influence of a conductive pollutant film on the capacitance signal can be eliminated by selection of at least one suitable measuring frequency. Furthermore, by optimizing the electrode height h, a large capacitance jump is achieved for a digital liquid level display, and/or a largely continuous increase in capacitance is achieved for an analog liquid level display. The sensor is preferably used to determine the location of an interface between water and oil in a separator tank.
Despite their advantages, known systems are either inaccurate and unreliable, or complex and expensive. It can thus be seen that the need exists for a simple, inexpensive measurement device that accurately determines the quantity of fluid in a contained volume.
These and other objects are achieved by providing a measuring apparatus for measuring the volume of a contained fluid. The apparatus includes an exposure chamber adapted for exposure to head volume of a volume of the contained fluid. A displacement mechanism is connected to the exposure chamber such that the displacement mechanism is displaced in proportion to the amount of head volume in the contained fluid acting on the exposure chamber. A read mechanism is connected to the displacement mechanism. The read mechanism generates a signal corresponding to the amount of displacement of the displacement mechanism.
The exposure chamber can be provided as an elongate, flexible tube, and the displacement mechanism can be provided as a flexible membrane. The displacement mechanism can include a guide assembly connected to the flexible membrane. The guide assembly can include a cylinder with a guide piston mounted for reciprocal movement in the cylinder. A first seal assembly connects the flexible membrane to the cylinder, and a second seal assembly connects the flexible membrane to the guide piston.
The guide piston can be provided as a first piston element connected to the flexible membrane by the second seal assembly, and a second piston element connected to the read mechanism. A link element connects the first piston element to the second piston element. The link element can be configured as a rod member. A first ball-and-socket connection is located between the rod member and the first piston element, and a second ball-and-socket connection is located between the rod member and the second piston element.
The read mechanism can be provided as a linear encoder, such as a non-contact optical linear encoder.
The foregoing will become apparent to one of ordinary skill in the art when taken into consideration with the following detailed description in conjunction with the following drawings, in which: